WO1996029544A1 - Combustion grate and process for optimising its operation - Google Patents

Abstract

The combustion grate is fully or partly gas and liquid-cooled via a control circuit. Here, the regulating value may be the grate temperature, the temperature of at least one grate bar or the combustion air temperature, especially the under-grate blast temperature. The reference value for the control circuit is the cooling water flow rate per unit time and/or the cooling water temperature. The control circuit is closed. Such a combustion grate makes it possible to obtain the best possible operation for a wide variety of fuels so that certain parts, especially grate components, of such installations bear virtually no stresses and have a long useful life.

Description

Combustion grate and method for optimizing the operation of a combustion grate

The present invention relates to a combustion grate and a method for optimizing the operation of a combustion grate.

It is known that for the combustion of different fuels, such as household waste, industrial waste, wood waste, solid, porous and liquid fuels and fuels with high and low ignitability, preferably combustion chambers are used, which are caused by mechanical rust and by cooled or uncooled fireproof side walls are formed.

Systems of this type have the disadvantage that their operation cannot be optimally designed for each of the fuels and therefore certain, in particular rust parts of such systems have faults and short lifetimes.

Grate coating cooling is also already known, such as the cooling of the grate covering by the combustion air flowing past in the air funnels or the forced cooling of the grate covering by the combustion air, which is pressed into the combustion chamber through a space which is formed from the grate bar and a baffle .

These known types of cooling are dependent on the amount of combustion air, and the air outlets in the combustion chamber can be blocked by ash, solid metals or slag. The cooling of the corresponding covering is therefore no longer ensured. This can lead to malfunctions. At the same time, these are Types of cooling have the disadvantage that the amount of combustion air primarily has a process function and does not have to perform a cooling function. Changing the amount of combustion air depending on the cooling effect is not always feasible. In this case too, the cooling effect of the grate covering is not guaranteed.

Water cooling of the grate is also known, the amount of water intended for the grate cooling keeping the grate at an approximately constant temperature, regardless of the calorific value of the fuel. This is again a disadvantage when burning fuels with a lower calorific value because heat is extracted from the combustion chamber. In this case, a higher cast coating temperature would be advantageous for the combustion.

The present invention aims to remedy this disadvantage.

In this sense, the combustion grate according to the invention and the method for its optimal operation are characterized by one of the claims.

The invention is subsequently explained, for example, using a drawing.

Show it:

1 is a cooling diagram for an air / water cooled combustion grate with control loop,

2 is a side view of a feed grate,

3 shows a representation analogous to FIG. 2 of a rust zone, on an enlarged scale, 4 shows a section along section line IV-iv of FIG. 3,

5 is a perspective view of an air /

Water-cooled grate bar in side view from the front, with parts broken away,

6 is a perspective view of the air / water cooled grate bar according to FIG. 5, in side / rear view,

Fig. 7 a turning grate bar with lifted side wall and metal hose connecting lines.

The invention is illustrated in FIGS. 1 to 7 on an air / water-cooled combustion grate, which is designed as a feed grate in terms of function. However, the invention can be easily applied to other grate designs, such as pyrolysis grate, degassing grate, gasification grate, combustion grate, high-temperature combustion grate, cooling grate, transport grate, counter-running grate, counter-overflow grate, push-back grate, roller grate and the like. like.

The feed grate 1 shown schematically in FIG. 1 serves to transport the fuel and the slag resulting from the combustion through the combustion chamber and, at the same time, to function as a combustion air distribution device.

The grate consists of several zones which are arranged horizontally or inclined. The individual zones can be on the same level or separated by a fall.

Each individual grate zone consists of fixed and movable grate steps with fixed grate bars 3 and movable grate bars 2. The movable steps are pushed back and forth with a variable number of strokes, whereby the fuel is transported. is turned and turned. The number of strokes depends on the fuel and the combustion process. The combustion takes place in the fuel layer, through which the combustion air, so-called underwind, is blown into the combustion chamber from below through gaps in the grate covering 22 (FIG. 2). The combustion air, which is operatively connected to the control circuit via a heat exchanger, simultaneously serves to cool the grate covering 22. The gaps between the individual grate bars 2 and 3 must be so small that as little as possible unburned small parts can fall through. These gaps are all evenly distributed over the entire grate surface.

The stroke length and the lifting speed of the movable grate covering 22 of the individual grate zones 20 are set as a function of the heat release on the grate 1 or in the combustion chamber.

The function of the grate covering 22 is thus defined as follows:

The grate covering 22 conveys the fuel through the combustion chamber.

The grate covering 22 serves as an air distribution device for the downwind.

The grate covering 22 is exposed to high thermal stress and, due to the high purchase costs and long downtimes during possible repairs, has a long service life and great operational reliability.

The cooling liquid for the feed grate 1 is supplied via distributor 5 and, after the grate bars 2 or 3 have flowed through, is collected in collectors 6 and returned. Not only water can be provided as the cooling liquid, but in particular also liquids with higher boiling points, for example certain oils. However, it is also possible to use the control system shown in FIG. 1 to add the liquid heat up and, if necessary, give off heat to the grate when passing through the feed grate 1.

1 shows that this water or the liquid flowing through the grate can be cooled or heated in a heat exchanger.

Another heat exchanger in the water network is used to heat or cool the downwind. By attaching a temperature sensor or a temperature measuring point, a desired temperature in the combustion chamber, in particular the temperature of the underwind, can be measured after leaving the grate 1. The temperature of the underwind can be increased or decreased by appropriate regulation of the liquid medium flowing through the grate, depending on the control program provided, which in particular has to be adapted to the specific type of fuel.

This has the great advantage that the underflow temperature can be changed within the intended limits with the flow medium, without the underwind quantity being influenced thereby.

In the cooling water diagram according to FIG. 1, the necessary flow fittings are also provided in order to carry out corresponding bridging (bypass) of control parts and thus to switch them off.

The coolant flow is marked by corresponding arrows.

2 shows the feed grate 1, which has three grate zones 20. The grate bars 2 and 3 are mounted on grate slides 21 and have a grate covering 22 facing the combustion chamber. Air funnels 23, which define air zones 24, are provided on the underside of the feed grate 1. 3 shows an enlarged side view of a grate with fixed grate steps 27 and movable grate steps 28. A supply line 30 is used for supplying the coolant to the fixed grate steps and a supply line 31 for supplying the coolant to the movable grate steps 28. Fig. 3 also shows a feed water cylinder 33, which takes into account the displacements of the movable grate steps 28.

4, which shows a section through the grate according to FIG. 3 along section line IV-IV, the two feed lines 30 and 31 can also be seen. In addition, the drain lines 35 and 36 for the flow medium are shown.

5 and 6 show a perspective view of details of an air / water-cooled grate bar in a simple design. It can be a movable grate bar 2 or a fixed grate bar 3. This grate bar with the grate covering 22 has a dividing wall 40 in its interior, so that a first cooling chamber 41 and a second cooling chamber 42 lying parallel thereto are formed in the longitudinal direction. At the front end of the grate bar 2 or 3 there is a water flow opening 43. This creates the connection between the two cooling chambers 41 and 42. In each of these cooling chambers there is a corrugated baffle plate 45 which is arranged parallel to the partition 40 and which increases the heat exchange.

The grate bars 2, 3 are pivotally mounted on a grate shaft 46. Immediately below the grate shaft 46 is a distributor 48 which supports the grate shaft 46 and below this a collector 47 which, in conjunction with the cooling water supply line 50 and the hot water return line 51, ensure the flow of the coolant through the grate rod. Due to the large temperature differences occurring on the grate in the use and non-use state and as a result of the movements of the grate bars 2, the cooling water supply and return lines 50 and 51 are provided with helical spring-shaped windings, so-called temperature compensation elements 52.

Because of this arrangement, the cooling system is kept tight at the connection points both in the idle and in the operating state.

FIG. 7 shows a turning grate bar 60 which is pivotably mounted on a grate bar support 61. A supporting coolant distributor 62 is also located underneath this grate support 61, combined with a collector 63. The one cooling chamber 65 is equipped with a corrugated baffle plate 66. In this case, a connection line 68 consisting of a metal hose is provided, which ensures connections free of thermal stress for the flow medium.

Since it is a so-called turning grate bar 60, a bearing shell 70 is also provided at its front end, so that, according to any uneven wear of the grate covering 22, the turning grate bar 60 is rotated and the front bearing shell 70 onto the grate bar carrier 61 can be set. Corresponding connection and connection points are provided at the front end of the turning grate bar 60, as can be seen.

With the described system and the intended control circuit, the influence of thermal overloads of the combustion grate is limited locally or on the entire grate surface by means of the air / water-cooled grate covering in such a way that the known operational disturbances and wear of the grate cover can be largely excluded . This is due to the air / water cooling of the rust ges, as shown and explained in Fig. 1. The cooling takes place as a function of the cooling water quantity and the cooling water temperature as well as the heat release on the grate. For this purpose, as explained, the temperature control is achieved by means of a temperature sensor or temperature measuring system.

A further special feature of the invention is that when waste with a low calorific value is burned, the heat removed from the liquid circuit from the grate bar is released to the combustion air by means of heat exchange between grate bar and combustion air, which is very intensive due to the geometric shape of the grate bar and thus the combustion of the garbage lying on the grate is accelerated.

When burning garbage with a high calorific value, a larger amount of heat is removed from the corresponding grate parts by the cooling liquid, whereas when burning garbage with a low calorific value, less heat is dissipated in the grate covering, which in order to accelerate the combustion process in any case, is used for heating the combustion air. The greater transfer of heat to the combustion air and thus the increase in air temperature is achieved by reducing the amount of cooling water due to the smaller specific heat release occurring on the combustion chamber side than the heat release on the grate and thus increasing the temperature of the cooling water more. This means that there is increased heat emission from the grate bar to the combustion air.

In this way, the cooling creates advantages in the combustion of waste with a high, but also with a low calorific value, since the heat removed can be fed back into the combustion air if required.

In this sense, it is novel to usefully separate the cooling function and the process function and thus to result in a process-related change in the amount of combustion air under the grate (underwind), the effect of the grate cooling is influenced so that largely no faults can occur.

Claims

Claims: 1. Combustion grate, characterized in that it is completely or partially both gas and liquid cooled via a control loop. (Fig. 1) 2. Combustion grate, preferably according to at least one of the claims, as in claim 1, characterized in that the control variable is the grate temperature. 3. combustion grate, preferably according to at least one of the claims, as in claim 1, characterized in that the controlled variable is at least one grate bar temperature. 4. Combustion grate, preferably according to at least one of the claims, as claimed in claim 1, characterized in that the controlled variable is the combustion air temperature, in particular the underwind temperature. 5. Combustion grate, preferably according to at least one of the claims, such as according to one of claims 1 to 4, characterized ge indicates that the manipulated variable of the control loop is the cooling water flow rate per unit time and / or the cooling water temperature. 6. combustion grate, preferably according to at least one of the claims, such as according to one of claims 1 to 5, characterized ge indicates that the control loop is closed. 7. combustion grate, preferably according to at least one of the claims, such as according to one of claims 1 to 6, characterized ge indicates that liquid-carrying, in particular moving Lines (50, 51) are equipped with thermal expansion compensation means (52), in particular with helical spring-like windings. 8. combustion grate, preferably according to at least one of the claims, such as according to one of claims 1 to 7, characterized ge indicates that liquid-carrying connecting lines are designed as metal hoses (68). 9. Combustion grate, preferably according to at least one of the claims, such as according to one of claims 1 to 8, characterized ge indicates that the control circuit has at least one temperature consumer for the combustion air, which acts on a liquid quantity or temperature controller. (Fig. 1) 10. Combustion grate, preferably according to at least one of the claims, such as according to one of claims 1 to 9, characterized ge indicates that the control circuit has at least one heat exchanger for the cooling liquid and preferably one for the combustion air. (Fig. 1) 11. Combustion grate, preferably according to at least one of the claims, such as according to one of claims 1 to 10, characterized in that the control circuit has a circulating pump and at least one control valve in the liquid circuit. (Fig. 1) 12. Combustion grate, preferably according to at least one of the claims, such as according to one of claims 1 to 11, characterized in that a bypass is provided in the control loop. (Fig. 1) 13. combustion grate, preferably according to at least one of the claims, such as according to any one of claims 1 to 12, characterized in that the grate bars (2, 3) corrugated exchange shear (45). 14. Combustion grate, preferably according to at least one of the claims, such as according to one of claims 1 to 13, characterized in that distributors (47, 48) are designed as supports for carriers (46). 15. Combustion grate, preferably according to at least one of the claims, such as according to one of claims 1 to 14, characterized in that grate bars are formed as interchangeable bars (60). 16. A method for optimizing the operation of a combustion grate, preferably according to at least one of claims 1 to 15, characterized in that one or more temperature meters are attached in the area of the gas-loaded grate to determine their temperature for regulating the flow rate per unit of time and / or the temperature of a grate bars used directly brushing liquid. 17. The method, preferably according to at least one of the claims, as claimed in claim 16, characterized in that a flow meter for the liquid and a heat exchanger are arranged in the control circuit. 18. The method, preferably according to at least one of the claims, as claimed in one of claims 16 or 17, characterized in that the grid is gas-washed and liquid-flushed and the liquid is used to control the temperature of the grid or the grid circulating gas temperature control.